Credit: Nancy Lane

As city and state leaders urge all Bay Staters to get their flu shots as soon as possible, epidemiologists are scrambling to get to the roots of this year’s especially potent flu outbreak, which has been blamed for at least 18 deaths in Massachusetts since October.

“It’s here and it’s early,” said Bill Hanage, an epidemiologist at the Harvard School of Public Health. Hanage attributed this year’s “moderately severe” flu season to the H3N2 strain of the influenza virus.

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